Many applications require that one article, structure or item be bonded or adhered to another article, structure or item. For example, anchor bolts are employed in various fields of engineering and construction as strengthening or reinforcing members in rock formations, or concrete or masonry structural bodies. The bolts, which are typically metallic, are inserted into holes, gaps or openings in the rock formations, or concrete or masonry structural bodies, and are fixed or anchored therein by means of an anchor composition. Objects that have been attached to concrete or masonry using anchor bolts include, but are not limited to, electrical conduits, panels, piping and wall sections. Adhesive anchors are preferred over mechanical anchors for anchoring in soft concrete or masonry because, among other reasons, adhesive anchors place less stress on the concrete or masonry. As used herein, the term “masonry” shall include, but is not limited to, stone, brick, ceramic tile, cement tile, hollow concrete block and solid concrete block. Typically, the anchor composition cures or hardens (polymerizes) to form a strong bond between the rock formation, or the concrete or masonry structural body, and the bolt.
It has been known to use curable synthetic resins as the primary adhesive for the safe fastening of anchoring rods, bolts and similar devices in solid rock, masonry, concrete and the like. Typically, but not exclusively, certain of the starting components of the adhesive composition are kept separate from one another and then combined at or near the point of fastening. In such so called two part systems, the components which are kept separate until the time of use are combined at the site and then introduced to the anchor bolt, the bore or hole prepared to receive the bolt, or both. Thus, the formation of the cured adhesive body that binds the fastener to the base structure is initiated at about the time the fastener is placed in its final position.
A useful anchor composition should provide a strong bond between the concrete or masonry and the material to be anchored to the concrete or masonry, be easy to dispense at the location of use, and is preferably not noxious or offensive to the user. It is also-preferred in certain embodiments that the adhesive is capable of achieving a substantial portion of its ultimate strength in a relatively short period of time. This last feature can be critically important to the commercial success of the adhesive since it can allow a construction project to proceed at an efficient and profitable pace. Moreover, applicants have noted that in many applications it is desirable for the adhesive to be capable of achieving good bonding properties even if it is used or applied during inclement weather, during cold weather, or under other conditions, which produce substantial moisture and/or low temperatures at the bond site.
Many of the curable adhesive compositions currently used in the industry, and in particular the field of anchoring in or to concrete, rock, and like materials, are based on compounds that are polymerized or cured by condensation and/or ring-chain conversion polymerization of monomers, oligomers, prepolymers and like compounds that have at least one functional group, typically at least one functional group along the polymer backbone, such as hydroxyl groups, and at least one terminal functional group, such as oxide groups. For example, epoxy-based adhesive compositions are typically cured by one or more of these mechanisms. The epoxy resin and a curing or hardening agent are typically mixed immediately prior to use, and cure within a certain amount of time.